1. Field of the Invention:
This invention relates to an apparatus and method of sealing tubes, particularly insulation tubes made of ceramic or glass, in which an electronic or electric device such as a resistor is inserted, under air-tight condition.
2. Description of the Prior Art:
The sealing of insulation tubes made of ceramic or glass in which an electronic or electric device, such as a resistor, being used for an application requiring high insulation and excellent flame and smoke resistance, in inserted under air-tight or vacuum conditions, is a well-known practice. Heretofore, in such air-tight sealing of insulation tubes containing a resistor or the like, a metalized layer, which is usually formed by coating and calcining a silver paste, is placed on the inner surface of both ends of the insulation tube so as to be solderable, and then a solder for sealing is placed on the metalized layer on the inner surface of the insulation tube, and this solder is then heat-melted to cause to be distributed on the sealing part a drench of the solder or an acid or flux. However, it takes a long time to distribute the solder on all of the required area utilizing this method. Accordingly, the metalized layer formed on the insulation tube or on the wall of the resistor is damaged by heat or flux, whereby disadvantages due to incomplete sealing and decrease of desirable characteristics as outlined above are caused.
It has therefore been proposed to seal insulation tubes by forming the metalized layer on an inner surface of the tube, placing the solder on the metalized layer on the inner surface of insulation tube, heat-melting the solder and rotating the insulation tube about its axis, whereby the molten solder can be distributed on the peripheral sides to cause drenching thereof due to a centrifugal force.
However, this process has heretofore been carried out only by hand and, accordingly, there are various disadvantages incurred because it is difficult to supply an optimum amount of solder and to prevent fluctuation of the temperature and the time needed for heat-melting the solder, whereby a loss of the sealed products is high.